As is known, currently automatic lawn mowers are predisposed to operate within predetermined cutting areas.
Lawn mowers are utilized to keep lawns, gardens and grassy areas in general, in optimal condition, that is, to keep the grass below a certain height in a substantially homogeneous manner throughout the entire cutting area.
The cutting area is often delimited by a perimeter wire or cable, in which an electrical signal is propagated; the lawn mower, detecting this electrical signal, is capable of recognizing the boundaries of the cutting area and adjusting its own movement and/or cutting activities accordingly.
As is known, lawn mowers are equipped with an independent electrical power supply unit, which has the function of supplying electric power to the electrical and electromechanical devices present inside the lawn mower itself, such as, for example, the motors designed to drive the wheels and the blades, the electronic circuits dedicated to detection of the presence of grass, to detection of the presence of the perimeter cable, to the processing of the data collected and to controlling the various motors, etc.
When the power supply unit, which is typically made up of a battery or a battery pack, nears exhaustion, the lawn mower goes to a recharging base, where the power supply unit can be recharged so as to permit, after a certain amount of time, continuation of the activity of the lawn mower.
In the name of the same Applicant, the European patent application no. 11425071.5 has been filed describing a particular technique for re-entry to the recharging base, according to which the lawn mower follows a path consisting of a sequence of arcs having the ends thereof positioned, approximately, on the perimeter wire.
This solution undoubtedly offers a series of advantages, among which that of minimizing the probability of the lawn mower passing over the same area several times, damaging the grass that is situated there.
Yet, while continuing the research activity, the Applicant found that the arc paths also involve some drawbacks:
the route that the lawn mower follows to re-enter to the base is decidedly longer with respect to a theoretical rectilinear path, and therefore leads to waste in terms of time, and also in terms of the power consumed by the lawn mower;
in order to describe arc paths, the wheels of the lawn mower are activated in a substantially alternating manner (to turn right, the left wheel is activated, while the right wheel remains stationary, and vice versa), so that the lawn mower can never operate at maximum speed, which is clearly reached on rectilinear paths; this involves a further extension of the time required for re-entry to the recharging base; and
the fact that arc paths are followed, involves a significant task on the part of the mechanical and electrical/electronic structure of the lawn mower and, in the long term, more frequent and expensive maintenance activity may be required.